This invention relates to a device and a method for carrying out measurements on drilling debris or xe2x80x9ccuttingsxe2x80x9d, in particular continuously to measure, using the weighing principle, the flow rate of debris brought from the bottom of a bore drilled using a bit driven in rotation and with the help of a cleaning fluid.
Until now, within the expertise of a mud logger or a supplier of monitoring services for information revealed by means of the circulation fluid used during drilling, the data relating to the spoil are restricted to an imprecise observation at a point in time of the pieces of rock brought to the surface which are collected by the site geologist at regular intervals at the outlet from a vibrating screen. It is therefore impossible to examine trends relating to the flow rate of the spoil: the flow rate can diminish if the cleaning of the bore is not sufficient, the flow rate can increase if the walls of the bore collapse or if the diameter of the drilling is increased.
The purpose of this invention relates to a system capable of informing us, at the surface, about the instantaneous mass and/or volume flow rate of rocks drilled by a drilling bit.
Document U.S. Pat. No. 4,413,511 is known which describes a system of continuous measurement of the volume of drilling spoil and the quantity of drilling fluid transported with this spoil. This system does not have the same objective as this present invention and is structurally different, notably with regard to the measurement means which use tubs filled with a fluid, the variation in the level of which is continuously measured.
Hence, this invention relates to a device for measuring the flow rate of spoil from a drilling brought to the surface by means of a drilling fluid. The device comprises means for collecting the spoil and means of continuously measuring the weight of spoil collected. In the invention, the means of collecting the spoil comprise a receptacle in the shape of bucket, pivoting about one axis and means of tilting the receptacle in such a way that the bucket is emptied and the measurement means comprise a measuring cell connected to the tilting means in order to measure a stress substantially proportional to the weight of the spoil collected.
The tilting means can comprise a shaft rotating on two bearings, a pneumatic jack connected to said shaft, and a component connecting said jack to a fixed base.
Said measuring cell can be arranged on said connecting component.
The cell can measure a bending stress of the connecting component, said stress being substantially proportional to the weight of the spoil collected.
The tilting means can comprise pneumatic components with command logic for the sequence of operations for said tilting means.
The invention also relates to a method of measuring the flow rate of drilling spoil brought to the surface by a drilling fluid wherein the following steps are carried out:
a) the spoil is collected continuously in a receptacle for a defined period of time,
b) said accumulated spoil is continuously weighed during said period,
c) said receptacle is emptied at the end of said period,
d) operations a) and b) are repeated
e) the spoil weights are accumulated by means for processing the measurement
f) calculation of the spoil flow rate is carried out
g) the spoil flow rate measurement is processed in order to calculate and/or to record at least one of the following parameters: the flow rate of the spoil as a function of time, the ratio of the flow rate of the spoil to the rate of penetration, the ratio of the measured flow rate of the spoil to the theoretical flow rate of the drilled spoil, the difference between the measured flow rate of the spoil and the theoretical flow rate of the drilled spoil.
In the measurement method, the parameters can be expressed as a function of the mass flow rate.
In a variant, one can measure the density of the spoil collected.
In the preceding variant, the density of the dry spoil can be measured, that is to say, after removal of the drilling fluid.
The parameters can be expressed as a volume flow rate by using at least one of the measurements of the density: before or after removal of the drilling fluid.
With the purpose of making use of the measurement of the spoil flow rate, this device has been developed from research into two main applications:
a) To be able to display
a provisional image of the profile of the bore
the trend to either exceed or to fall short of the theoretical drilled volume.
b) To be able to correlate this image with the real context of the drilling operations under way, in order to know the influence of certain drilling actions on the behavior of the measurement of the mass or volume flow rate of the spoil.
Through this new measurement of volume or mass flow rate of the spoil, an observation of the historical returns is available put back into its drilling context (behavior and measurement trends, reproducibility of the observed phenomena).
The driller is thereby given the means to optimize the cleaning of the bore or to diagnose instability of the walls.